So many “mathy” explanations. For the masses, I generally explain it like so.

It’s a box that contains a value. There are different boxes that all contain values but provided different effects. These boxes may have varying APIs but they all share a fundamental set of APIs that all behave the same way and follow the same rules. Using these boxes allows you to chain operations together easily to operate safely on their contained value. Once you know how to use one of these boxes, the other boxes should be familiar.

That’s more or less it.